Method of manufacturing inner tubes



y E69 1950 F. A. MULBARGER ETAL 2,507,865

METHOD OF MANUFACTURING INNER TUBES Filed Nov. 16, 1945 INVENTOR FRANCES J LMULEARGER BY HERBERT BJHATT ATT(%EY Patented May 16, 1950 UNITED STATES PATENT OFFICE LIETHOD OF MANUFACTURING INNER TUB Francis A. Mulbarger and BerbertD. Hiatt, In-

dianapolis, Ind., assignors to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application November 16, 1945, Serial No. 629,090

Claims.

of the tube stock together in spliced relationcompositions are synthetic rubbers and particularly Butyl or GR-I compounds produced by the I copolymerization of .isobutylene and butadiene.

Some types of inner tubes because of their composition result iii-thinning of the stock adjacent to the splice due to subsequent handling operations. This in part is due to the additional heat applied in the use of the hot trimming knife. Also the clamping mechanism applied during the trimming operation exerts a pressure 'on the walls of the tube to cause a displacement of the plastic composition. It has been found that this condition may be remedied to some extent by allowing the spliced inner tubes to rest for a period of time up to a few hours during which a recovery would take place eliminating the localized thin spots. When it is required to store inner tubes for this purpose a considerable amount of space is required. Furthermore, additional difficulties are encountered. For ex ample, when an unvulcanized tube is folded back on itself and is allowed to rest for a given period a further injury and thinning out of the walls of the stock takes place at the double fold in the hinged portions of the folded tube. This can be avoided if the rest and recovery period to which the tube is subjected is reduced. We have found that if the region of the splice of the inner tube is subjected to the influence of a low temperature, much of the difliculty in the processing of inner tubes can be avoided, in part, because the chilling tends .to preserve the strains in the 'tion, it has beenfound that the flow characteristics of the composition of the inner tubein the region of the splice may be materially reduced by positioning the spliced area of the inner tube-in.

direct contact with a refrigeration conduit, and preventing the accumulation of frost on the conduit by immersing the conduit, in part, in a liquid having a low freezing point and depending upon capillary action of the liquid to maintain the conduit in relatively frost-proof state. An arrangement of this kind locally increases the viscosity of the composition in the'region of the splice, therefore, the strength of the splice is increased while the remaining portion of the tube remains soft and is readily formable. After the-splice rests against the refrigeration conduit for a short period of time a suflicient recovery in the thickness of the material takes place and the inner tube may thereafter be handledand subjected to further processing without danger of thinning out in the region of the splice.

It is therefore among the objects of our invention to provide a, method of treating inner tubes in order to prevent separation at the tube splice; to provide a. method of treating tubes which avoids thinning out of the walls of the inner tube at localized areas; to provide a method of treating tubes which results in the formation of a strong splice; to provide a method of treating tubes which will permit the use of compositions which in the unvulcanized state are flowable at normal room temperatures; to provide such a method of treating inner tubes which requires very little storage space; and,-to provide such a method of treating inner tubes which may be economically and expeditiously carried on.

These and other objects and advantages of our invention are described in detail in the following description when considered in connection with the accompanying drawing; in which Fig. l is a perspective view, partly in section, illustrating a method of treating tubes in accordance with our invention; and

Fig. 2 is a transverse view in section taken along lines II--II of Fig. l.

With reference to the drawing, we show an apparatus with which the treatment of inner tubes in accordance with the practice of our invention may be conducted. Essentially this apparatus comprises a table-like structure i upon which inner tubes 2 may be laid. Extending longitudinally of the top of the table I is a conduit 3. As shown in Fig. 2, this conduit 3 is held in a fixed position in which the top of the conduit lies in a position above the top of the table I. The purpose of this difference in elevation is to insure that the butt splice 4 will rest firmly against the conduit 3 when the inner tube 2 is laid upon the table.

The conduit 3 is connected to a conventional refrigerating unit so as to induce a low temperature throughout the length of the conduit for example, from 32 to 0 Fahrenheit. When a conduit of this type is operating under normal temperature and humidity the exterior surface of the conduit becomes covered with frost and. accordingly, there is a corresponding reduction accuse in the transmission of low temperatures to the inner tubes. Ordinarily it is necessary to defrost the conduit frequently in Order to maintain its maximum efliciency. In order to avoid or reduce the necessity of frequent defrosting of the conduits, we provide a trough i positioned below and extending along the length of the conduit 8. This trough 5 is filled with a liquid 0 having a low freezing point. This conduit 8 is partly submerged throughout its length in the liquid 0 with the result that capillary action causes the liquid to extend over the surface of the conduit thereby preventing a formation of any appreciable amount of frost. Various materials of low freezing point may be utilized for the liquid 0. Examples of such materials are alcohol, kerosene, brine solution, glycerine or other similar operable materials.

In the practice of our invention inner tubes are extruded in the conventional manner, trimmed to proper length and the ends of the tube joined together in butt relationship. Directly after this operation the inner tubes 2 are manually removed from the butt splicing operation and are laid on top of the table I in such manner that the region of each splice lies in direct contact with the conduit 3. The resulting effect is that the tube in the region of its splice, which previously was warm or hot, becomes chilled. This reduction in temperature of the inner tube composition increases the viscosity of the inner tube composition and prevents deformations such as thinning of the stock due to plastic flow. Also, some recovery in thickness is caused by release of the strains in the composition. After the tube is allowed to remain in contact with the conduit for a period of from 5 to 20 minutes the inner tube may be removed and subjected to subsequent processing and vulcanization in accordance with the conventional practice of manufacturing inner tubes.

It is therefore believed apparent that we have provided a novel method of treating inner tubes in order to provide an eflicient and durable splice which results in many economies and improvements in the resulting product.

While we have shown a preferred method of practicing our invention it is to be understood that it is susceptible to these modifications which appear obviously within the spirit of the invention and as appearing in the scope of the appended claims.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. The method of manufacturing tubes of plastic composition comprising the steps of forming a length of tubular stock of plastic composition; trimming the ends of the stock to form a tube of predetermined length, pressing the ends of the length of stock together in adhered butt relationship to form a butt joint, and refrigerating the stock locally in the region of the joint whereby thinning of the stock in the region of the joint upon subsequent handling of the tube is substantially prevented.

2. The method of manufacturing inner tubes for pneumatic tires comprising the steps of forming a length of tubular stock of plastic composition, clamping the ends of the stock between clamping members, trimming the ends of the stock to form a tube of predetermined length, the ends of the length of stock together in adhered relationship to form a butt joint, and subjecting the stock in the region of the joint to the influence of a refri eratin conduit nfter unclamping the stock, whereby substantial recovery of the stock occurs to its original thickness before clamping, and thinning out of the stock in the area of the joint upon subsequent handling of the tube is substantially prevented.

3. The method of manufacturing inner tubes for pneumatic tires comprising the steps of forming a length of tubular stock of rubbery butadiene-isobutylene copolymer, trimming the ends of the stock to form a tube of predetermined length, pressing the ends of the length of stock together in adhered relationship, subjecting the stock in the region of the Joint to the influence of a refrigeration conduit, and maintaining the refrigerating conduit free from frost formation by the application of a liquid having a lower freesing point than water whereby the temperature of the stock in the region of the joint is substantially reduced and thinning out of the stock in the region of the joint upon subsequent handling is substantially prevented.

4. The method of manufacturing inner tubes for pneumatic tires comprising the steps of forming a length of tubular stock of rubbery butadiene-isobutylene copolymer, clamping the ends of the stock between clamping members, trimming the ends of the stock with a hot knife to form a tube of predetermined length, pressing the ends of the length of stock together in adhered relationship, subjecting the stock in the region of the resulting joint to the influence of a refrigeration conduit, after unclamping the stock, and maintaining the refrigerating conduit free from frost formation whereby substantial recovery of the thus refrigerated stock occurs to its original thickness before clamping, and thinning out of the stock in the region of the joint upon subsequent handling of the tube is substantially prevented.

5. The method of manufacturing inner tubes for pneumatic tires comprising the steps of fom ing a length of tubular stock of rubbery butadiene-isobutylene copolymer, trimming the ends of the stock to form a tube of predetermined length, pressing the ends of the length of stock together in adhered relationship, subjecting the stock in the region of the resulting joint to the influence of a refrigerating conduit, and maintaining the refrigerating conduit in contact with a liquid having a lower freezing point than water whereby the liquid by capillary action traverses the surface of the conduit and prevents frost formation on the conduit allowing the inner tube stock to rest in direct contact with the refrigerating conduit so that the temperature of the stock in the region of the joint is substantially reduced and thinning of the stock in the region of the joint upon subsequent handling of the tube is substantially prevented.

FRANCIS A. MULBARGER. HERBERT D. HIATT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,177,678 Bierer Apr. 4, 1918 1,382,207 McGuire June 21, 1021 1,802,491 Young et al Apr. 28, 1031 2,024,578 Haase Dec. 17, 1035 2,188,286 Engler et al Jan. 9, 1940 2,231,769 Merril Feb. 11, 1041 2.2'13 M flnmnhnll A Q LL on In. 

